A blog by the Santa Clara Valley Water District to track work and community input
In 1982, the city of San Jose opened Almaden Lake as a public park and for some time, offered activities such as fishing, swimming and pedal boating. With its sandy beach, it became a popular spot for picnics and summer festivals, a gathering place for the community.
But despite its surface beauty, the lake tells a different story below its waters. In pockets of the 32-acre body of water, where depths plunge to more than 35-feet, elemental mercury is methylizing into a toxic form. Waste from Canada Geese and seagulls have rendered it unusable for recreational swimming. And the man-made lake that was once a gravel quarry is actually damaging the ecological structure of the area, serving as a heat barrier to cold-water fish migrating upstream to spawn.
The Santa Clara Valley Water District must act, both from the perspective as an environmental steward of the Guadalupe Watershed to offset impacts to cold-water fish and from a mandate by the San Francisco Regional Water Quality Control Board to control the production and release of methylmercury from Almaden Lake.
As of March 13, the water district’s project team is evaluating four alternatives identified as being feasible to reduce the impacts from mercury containing sediment to water quality and habitat and high water temperatures to cold-water fish. Two of the original six proposed alternatives did not advance; One called for a 100-foot wide restored creek with a 22-acre lake and 5-ace wetland planting area but fell because of concerns that wetlands may increase mosquitoes in a residential area, while the other suggested to keep the lake as is.